Modular motor drive communication system and method

ABSTRACT

A motor drive system includes a control module and a power module for generating control signals and power signals, respectively, for driving an electric motor. An add-on module or subassembly is physically positionable between the control and power modules, and communicates with the control module to allow for communication with external devices.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of U.S.Provisional Application Ser. No. 61/946,408, entitled “MODULAR MOTORDRIVE COMMUNICATION SYSTEM AND METHOD”, filed Feb. 28, 2014, which ishereby incorporated by reference in its entirety.

BACKGROUND

The present invention relates generally to drive systems for poweringelectric motors, and more particularly to a modular drive systemdesigned and adapted for controlling motors of various sizes andratings.

A myriad of applications exist in industry for electric motors ofvarious types. In many applications, induction motors are driven torotate loads, such as pumps, fans, and conveyors, to mention only a few.Other types of motors may similarly be driven. A load may call foruniform speed and torque throughout its life, although many applicationsrequire much more flexible control. That is, a motor may need to bedriven at different speeds and with different torques at differentstages in its operation. To accommodate such needs, variable speed motordrives have been developed that allow for output waveforms of varyingand controllable frequency, capable of correspondingly varying thespeeds of driven motors. Similarly, equipment has been developed forsoft starting motors, starting and stopping motors in controlledmanners, and so forth. Such motor drives are now ubiquitous throughoutindustrial, commercial, shipping, material handling, and otherapplications.

In general, motor drives are designed to provide good service life in arange of conditions and with a range of loads. The drives may bedesigned around a single package that can be programmed and wired toreceive input power as well as to output conditioned power to theelectric motor. Such packaged products typically include powerconditioning circuitry that receives alternating current (AC) input andconverts the AC input to a direct current (DC) form, before reconvertingthe DC power to controlled frequency AC output. Various operatorinterfaces and programming platforms may also be provided, as well asnetworking capabilities.

One particular challenge that arises in such products is the design forvarious motor sizes, for facilitating programming, for sharingprogramming and control parameters, and so forth. Most such productshave been designed to power specific sizes of motors (typically rated bythe power output or frame size), and the user must select and programthe appropriate product for the particular motor to be powered. All ofthe circuitry used to control power electronic devices within the driveshas typically been included in the single package. Programming has beendone either manually or by an interface with a configuration computer ornetwork connected to the unitary package. This product paradigm,however, suffers from drawbacks including limitations of installationand configuration of the drives, relatively inefficient use of controlplatforms between drives, in accessibility of the programming once thedrive is commissioned, or, conversely, risks of access to the drivesfrom exterior sources due to resident network connections.

One novel approach now being taken for motor drives involves design andconstruction of “modules” that are interfaced to provide the desiredcontrol and power. In some such designs, control modules orsub-assemblies are paired with power modules or sub-assemblies, withcommunication between the two, once interconnected, to provide thedesired control signals for the power components, and to providefeedback for the control components. Some designs incorporate native orintegrated communications circuits that allow for communication withexternal or remote devices, such as for programming the drives, alteringsettings, monitoring operation, or communication and coordination withother drives. However, such designs generally do not allow forretrofitting or optional incorporation of such communications hardware,firmware or software.

There is a need, therefore, for improved techniques for driving electricmotors that can respond to such drawbacks.

BRIEF DESCRIPTION

The present disclosure sets forth a motor drive system including amodular power subassembly controllable to provide controlled frequencyAC power to an electric motor, and a modular control subassemblyseparable from the power subassembly control circuitry that, inoperation, applies control signals to the power subassembly forcontrolling the provided power. An add-on subassembly is positionablephysically between the power subassembly and the control subassembly andelectrically coupled to the control subassembly for providingcommunication between the control subassembly and at least one externaldevice.

The disclosure also sets forth a motor drive system including acommunication subassembly configured to be positioned between a controlsubassembly and a power subassembly of the motor drive system. Thecommunication subassembly is electrically coupled to the controlsubassembly and provides communication between the control subassemblyand external devices.

Further, in one embodiment, a motor drive system includes a modularpower subassembly controllable to provide controlled frequencyalternating current power to an electric motor, and a modular controlsubassembly separable from the power subassembly and that, in operation,applies control signals to the power subassembly for controlling theprovided power via a first mating connector of the modular powersubassembly connected to a second mating connector of the modularcontrol subassembly. A communication subassembly is only physicallycoupled and electrically coupled to the control subassembly forproviding communication between the control subassembly and at least oneexternal device. The communication subassembly is configured to fitaround the mated first and second mating connectors when the modularcontrol assembly and the modular power subassembly are attached so thatthe communication subassembly is positioned between the modular controlsubassembly and the modular power subassembly.

DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view of an exemplary motor drive system inaccordance with aspects of the present techniques;

FIG. 2 is a similar perspective view of the system of FIG. 1 with acontrol sub-assembly removed from a power sub-assembly;

FIG. 3 is a perspective view of the control sub-assembly and powersub-assembly illustrating internal plug-in connectors for mating the twoand for the exchange of signals between the two;

FIG. 4 is an exemplary illustration of how the same control sub-assemblymay be used with different power sub-assemblies having differentratings;

FIG. 5 is a diagrammatical representation of certain of the functionalcircuitry contained in the power sub-assembly, control sub-assembly, anda communication sub-assembly in a modified motor drive;

FIG. 6 is a perspective view of an exemplary motor drive systemadaptable to install the communication sub-assembly in accordance withaspects of the present techniques;

FIG. 7 is a partial perspective view of the system of FIG. 6 with thetop cover of the control sub-assembly unlocking the control sub-assemblyfrom the power sub-assembly;

FIG. 8 is a similar perspective view of the system of FIG. 6 with thecontrol sub-assembly removed from the power sub-assembly;

FIG. 9 is a perspective view of inserting an interface connector for thecommunication sub-assembly into a header located at the back of thecontrol sub-assembly;

FIG. 10 is a perspective view of installing the communicationsub-assembly by aligning it with the interface connector and connectingthe two;

FIG. 11 is a top view of the communication sub-assembly includingvarious components in accordance with an embodiment;

FIG. 12 is an exemplary illustration of a single-drive mode where asingle network node consists of a single drive with the communicationsub-assembly;

FIG. 13 is an exemplary illustration of a multi-drive mode where asingle network node consists of one to five drives where the first driveincludes the communication sub-assembly;

FIG. 14 is a table depicting a HSDSI packet format specification, inaccordance with an embodiment;

FIG. 15 is a sequence diagram of packet exchanges initiated by thecommunication sub-assembly;

FIG. 16 is a schematic diagram of timeouts used by the controlsub-assembly and the communication sub-assembly;

FIG. 17 is a flow diagram of a process for a messaging reset sequenceinitiated by the communication sub-assembly; and

FIG. 18 is a flow diagram of a process for a messaging reset sequenceinitiated by the control sub-assembly.

DETAILED DESCRIPTION

The modular motor drive, and communications circuitry and functionalitymay be generally based upon certain existing designs, such as those setforth in U.S. patent application Ser. No. 13/727,209, entitled “ModularMotor Drive System and Method,” filed on Dec. 26, 2012 by Tio et al.,which is hereby incorporated into the present disclosure by reference.The present disclosure relates to what may be interchangeably referredto as an add-on device, optional device, comm option, option card,option, or communication sub-assembly that can be used in conjunctionwith such modular motor drives. The device may, in certain embodiments,be “sandwiched” between the control and power modules, and may includeone or more processors, memory, and interface circuitry to allow forcommunication between the external device or devices (via a network) andthe circuitry of the control module. That is, the add-on device, in someembodiments, may include a communication device to enable communicationbetween the drive and external devices. Such communication may followany desired protocol, such as high speed drive serial interface (HSDSI),DeviceNet, EtherNet/IP, Modbus, and so forth.

An exemplary motor drive system 10 designed to power an electric motor,such as an induction motor, is illustrated in FIG. 1. The motor drivesystem 10 essentially consists of a power sub-assembly 12 and a controlsub-assembly 14 which is designed to be secured to and attached to thepower sub-assembly during operation. In some embodiments, as discussedin detail below, an add-on device, such as a communication sub-assembly,is installed between the power sub-assembly 12 and the controlsub-assembly 14. A mechanical interface 16 allows for mating of thesub-assemblies and the sub-assemblies may be held together in variousmanners, such as via snaps, fasteners, and the like. However, in apresently contemplated embodiment, the control sub-assembly 14 and thepower sub-assembly 12 are physically configured to allow the controlsub-assembly 14 to be secured to the power sub-assembly 12 viainterfacing surfaces, such that the control sub-assembly 14 may beattached and detached from the power sub-assembly 12 by hand and withoutthe use of tools. This ability to toollessly attach and detach thecontrol sub-assembly 14 greatly facilitates programming, reprogramming,commissioning and servicing of the system. An operator interface 18 isshown on a front face of the control sub-assembly 14 and may allow forcertain user interactions with the drive, such as to view configurationparameters, alter configuration parameters, view logs, history, errorand other codes, view certain operational parameters (e.g., currents,voltages, speeds), network configuration, and so forth. In a presentembodiment, the operator interface comprises an LCD module that supportsmultiple languages, and is able to display parameter codes followed bydynamic descriptions.

As shown in FIG. 2, the control sub-assembly 14 is removable from thepower sub-assembly 12, such as for configuration (programming),servicing, and so forth. The control sub-assembly 14 may be removed fromthe power sub-assembly 12 without disconnecting the power sub-assembly12 from either the power supply (e.g., upstream power circuitry) or fromthe electric motor once placed in service. Also, the communicationsub-assembly may be installed and/or removed easily for configuration,servicing, and the like by removing the control sub-assembly 14 from thepower sub-assembly 12. However, in some embodiments, when installing thecommunication sub-assembly, the power supply may be disconnected fromthe power sub-assembly 12.

In one presently contemplated embodiment, multi-conductor connectorsmate when the control sub-assembly is mounted on or attached to thepower sub-assembly. FIG. 3 illustrates the control sub-assembly 14removed from the power sub-assembly 12, and shows the multi-conductorconnectors 20 and 22 that interface with one another when the twosub-assemblies are brought together to transfer power and data betweenthe control sub-assembly 14 and the power sub-assembly 12. That is, inone presently contemplated embodiment, the control sub-assembly 14 doesnot contain the means for supplying its own power (e.g., a battery), butreceives power from the power sub-assembly 12 when the two areconnected. Moreover, the control sub-assembly 14 performs allcomputations, implements all control routines, and generates all controlsignals that are applied to the power circuitry within the powersub-assembly 12 (as described more fully below) via the multi-conductorconnectors. The connectors 20 and 22 are provided on sides of thecontrol sub-assembly 14 and power sub-assembly 12 that face one anotherand are exposed only when the sub-assemblies are separated, as indicatedby reference numerals 24 and 26. That is, the facing sides are notaccessible when the two sub-assemblies are mated.

Although FIGS. 1-3 illustrate a control sub-assembly 14 that isgenerally co-extensive with the power sub-assembly 12, it is presentlycontemplated that the same control sub-assembly 14 may serve toaccommodate various power sub-assemblies that increase in both size andrating. FIG. 4 illustrates three such arrangements. In the first, thecontrol sub-assembly 14 is shown over a power sub-assembly 12 which islocated behind the control sub-assembly 14, the two sub-assemblies beinggenerally co-extensive with one another. As indicated by referencenumerals 28 and 30, however, power sub-assemblies of larger sizes andratings may be coupled to the same control sub-assembly 14. The powersub-assemblies mate and interface in similar manners, and the circuitrywithin the control sub-assembly is designed to allow for motors ofvarious sizes to be driven without altering the hardware or circuitrywithin the control sub-assembly. Such larger sizes are accommodated onlyby configuration changes within the control sub-assembly 14. Inpresently contemplated embodiments, for example, power sub-sectionshaving ratings of 0.4 to 22 kW/0.5 to 30 hp at 400/480V, with globalvoltage classes of 110V, 200V, 400V and 600V may be accommodated by thesame control sub-assembly 14. However, other sizes and ratings may, ofcourse, be envisaged.

In accordance with presently contemplated embodiments, the powersub-assembly comprises power electronic devices (e.g., switches) thatregulate the conversion of power from a power source to controlledfrequency AC output for driving the electric motor. The controlsub-assembly, on the other hand, comprises processing capabilities,motor control routines, parameters utilized by the routines for motorcontrol, operator interface circuitry, and so forth to provide controlsignals for the power electronics of the power sub-assembly. The controlsignals are applied to the circuitry within the power sub-assembly basedon the motor control routines and any further processing in the powersub-assembly converts these control signals to timing signals fordriving the gates of power electronic switches within the powersub-assembly. The communication sub-assembly may include one or moreprocessors, memory, and interface circuitry to allow for communicationbetween the external device or devices (via a network) and the circuitryof the control sub-assembly 14.

This general topology is illustrated diagrammatically in FIG. 5. Asshown in FIG. 5, the power sub-assembly 12 is designed to receive powerfrom a power grid or main, or more generally from an input power supply.The power will typically be applied by conductors or busses, and thedrive system may be, where desired, mounted near or remote from anelectric motor that is driven by the system in operation. In certainembodiments and installations, the motor drive system 10 may be rigidlymounted in a cabinet, on rails, or in any suitable manner. The incomingpower may conform to various standards, depending upon the country orregion in which the system is utilized, but will typically providesingle or three-phase input power that is applied to a rectifier circuit32.

The rectifier circuitry 32 may be passive or active, and where desiredmay allow for regenerated power to be applied back to the power source(e.g., during deceleration or braking of the load). The rectifiercircuit 32 produces DC output that is applied to a DC bus 34. Variousconditioning and support circuitry, illustrated generally by referencenumeral 36 may be connected to the DC bus 34. As will be appreciated bythose skilled in the art, such circuitry 36 may include inductors,capacitors, resistors, and so forth. In general, inductors andcapacitors may be utilized to store energy in the DC bus 34, and tosmooth variations or ripple in the DC power, as well as to supply energyduring certain periods of operation. Resistors may be provided forbraking or dissipating energy, and so forth. DC power from the DC bus 34is applied to an inverter circuit 38, or more generally to a powerconverter circuit.

The inverter circuit 38 will typically include pairs of power electronicswitches, such as insulated gate bipolar transistors (IGBTs) associatedwith diodes. These power electronic switches are driven to allow powerto be drawn from the DC bus to form a synthetic sinusoidal output of acontrolled frequency. The output power is then applied to an electricmotor 40. While in many applications the drive system is configured todrive single or multi-phase AC motors, it should be noted that the drivesystem may be adapted for driving different motor types, such aspermanent magnet motors.

In the illustration of FIG. 5, the power sub-assembly 12 also includesdriver circuitry 42. The driver circuitry 42 acts based upon controlsignals received from the control sub-assembly to generate gate drivesignals that are applied to the power electronic switches of theinverter circuitry 38. Where a switched rectifier is provided, suchdriver circuitry, or a separate circuit may similarly apply signals tothe rectifier. The driver circuitry 42 may base the timing of the gatedrive signals upon any desired algorithm, such as utilizing triangularcarrier waves and other techniques generally known in the art. Finally,the power sub-assembly 12 may include various sensors, indicatedcollectively by the reference numeral 44, that detect feedbackparameters, such as voltages, currents, position (electric motor) and soforth during operation. Signals to and from the driver circuitry 42 andfrom the sensors 44 are provided to the control sub-assembly via themulti-conductor connectors discussed above.

As illustrated, the communication sub-assembly 46, mentioned above, isinstalled between the power sub-assembly 12 and the control sub-assembly14. In accordance with certain aspects of the present disclosure, thecommunication sub-assembly 46 includes programmed and operativecommunication circuitry 48. As illustrated, the communication circuitry48 directly interfaces and communicates data to the control circuitry 52of the control sub-assembly 14. The communication circuitry 48 generallyincludes one or more digital and/or analog circuits, processors,memories, interfaces, firmware, and/or software configurations. Forexample, the communication circuitry 48 may include a network interface50 that allows for improved communication between the controlsub-assembly 14 and any connected (networked) devices, such as externalcontrol and/or monitoring equipment, other drives, and so forth. Thenetwork interface 50 may include an Ethernet interface and be configuredto communicate via various industrial data exchange protocol interfaces(EtherNet/IP, DeviceNet, Modbus, Profibus, ControlNet).

In some embodiments, the network interface 50 of the communicationcircuitry 48 included in the communication sub-assembly, or optionalcommunications device (referred to as “comm option” herein), mayimplement a high speed drive serial interface (HSDSI) that providescommunication between the control circuitry 52 and any external devices.Such comm options may utilize an HSDSI protocol that allows for improvedperformance and reliability. In accordance with this disclosure, anddiscussed in more detail below, enhancements to the protocol includealtering the packet format, improved message sequencing, and improvedcommunication failure handling. Additionally or alternatively, thenetwork interface 50 may implement a parallel interface (e.g., sharedmemory) that facilitates the communication of data.

The control sub-assembly 14 as illustrated in FIG. 5 comprises controlcircuitry 52 designed to implement one or more motor control routinesbased upon programmed parameters stored within the control sub-assembly14. The control circuitry 52 may comprise any suitable processor ormultiple processors, including micro-processors, field programmable gatearrays, dedicated application specific integrated circuits, and soforth. Memory circuitry, indicated generally by reference numeral 54 isassociated with the control circuitry 52 and allows for storage of motorcontrol routines, parameters referred to by the routines, as well as avast array of other information that may be useful for controlling andmonitoring the motor 40.

An operator interface 56 is further coupled to the control circuitry 52to allow for access to certain parameters, for alteration of programmingand parameters, and so forth, such as via the operator interface 18illustrated in FIG. 1. One or more network interfaces 58 may be providedfor similarly accessing certain information from the drive system. Suchinterfaces may include an Ethernet interface or various industrial dataexchange protocol interfaces (e.g., DeviceNet, ControlNet, Profibus,Modbus, etc.). Ethernet capability allows the drive system to beintegrated into an EtherNet/IP infrastructure, and the use of a dualport Ethernet card may permit connectivity options such as device levelring networking. It should be noted that, in some embodiments, thenetwork interface 50 of the communication sub-assembly 46 enablesenhanced protocols (e.g., HSDSI) to be used that improved communicationwith the control circuitry 52 over using the network interface 58embedded within the control sub-assembly 14.

In accordance with this disclosure, the HSDSI protocol used may includesan altered packet format, improved message sequence, and improvedcommunication failure handling. For example, an advantage of theimproved HSDSI protocol is to convert the physical high-speed serialchannel into two logical channels, one for control data and one formessaging data. This split allows control to continue being updatedwhile a message transaction is being processed. Devices can always usethe most recent or “freshest” control data that the devices receive(assuming the packet passes the CRC check and the control valid bitsindicate that the control data is valid). Messaging is also simplified,with a change in the sequence number in the messaging data indicating anew message. This provides efficient notification of a new messagingrequest, easy matching of requests and responses, and a built-in retryfrom CRC failures or other communication errors, as discussed in detailbelow.

Technical advantages of the HSDSI protocol are independent control andmessaging, utilizing direct memory access (DMA), sequence count basedmessaging, flexibility between multiple industrial protocols such asEtherNet/IP, Modbus, DeviceNet and Profibus, and is compatible with bothsingle and multi-drive operation, as discussed below. Independentcontrol and messaging refers to how the protocol places control data(drive I/O) separate from messaging data, as opposed to approaches thatmight utilize messages that contain both in the same package. This is anadvantage because drives often process messaging data differently thancontrol data. Decoupling control from messaging allows both sides of theprotocol to deal with control data quickly and messaging data when thereis time. HSDSI overcomes the limitation of forcing control updates to beonly as fast as a device could process both the message and the controlbecause of independent messaging and control. The packet format andtiming are optimized to take advantage of a DMA channel present on manymicroprocessors. The DMA channel allows data to be sent and/or receivedin the background, minimizing the amount of time the processor mustspend handling communication. A fixed packet size is used to allow theDMA channel to be pre-configured to receive the entire packet. Timingrequirements are also in place to allow one DMA channel to switchbetween handling the transmission and receiving sides of the protocol.

Messaging is accomplished using a mechanism that repeats the most recentmessage transmission along with a sequence number to allow the otherside to detect an updated message. If the receiver cannot processanother message immediately, it can process the message on anotherfuture reception. Timeout, retry, and reset mechanisms are available tore-synchronize the devices on the interface if messaging communicationsbreak down. HSDSI can be translated to and from EtherNet/IP, DeviceNet,Modbus, Profibus and other digital serial interface (DSI) protocols. Theupstream network communicates with an add-on device (communicationsub-assembly 46) supporting one of the above protocols, which the add-ondevice may convert to HSDSI to communicate with the drive. It should benoted that the term “drive” and control sub-assembly 14 may be usedinterchangeably herein. The drive may then end up using that informationto communicate with a device on the DSI bus such as a HIM, serialinterface or multi-drive slave. The drive transmits packets only inresponse to packets received from the communication sub-assembly 46.Low-level and high-level timeouts attempt to allow orderly recovery fromcommunication errors.

Returning to the components of the control sub-assembly, a universalserial bus (USB) interface 60 is provided in the illustrated embodiment.While one or more of these interfaces may be accessible from outside thedrive system when assembled, in a presently contemplated embodiment thenetwork interfaces 58 are accessible when the control sub-assembly ismounted on the power sub-assembly, while the USB interface, which allowsfor file transfer and configuration of the drive system, is notaccessible unless the control sub-assembly is removed from the powersub-assembly. Where desired, the drive system may be protected by theuse of passwords or other security devices.

FIGS. 6-10 illustrate the installation process and/or retrofittingprocess to include the add-on device (e.g., communication sub-assembly46) in the motor drive system 10. As previously discussed, the add-ondevice may enable communication between the control sub-assembly 13 andat least one external device.

FIG. 6 is a perspective view of an exemplary motor drive system 10adaptable to install the communication sub-assembly 46 in accordancewith aspects of the present techniques. In some embodiments, the motordrive system 10 may be retrofitted to include the communicationsub-assembly 46 or the communication sub-assembly 46 may be includedduring motor drive system assembly. As previously discussed, the motordrive system 10 includes the control sub-assembly 14 connected to thepower sub-assembly 12 via mechanical interface 16. To install thecommunication sub-assembly 46, power may be disconnected from the powersub-assembly 12 and the control sub-assembly 14 is removed from thepower sub-assembly 12. As illustrated, catches 62 on both sides of thecontrol sub-assembly frame 64 may be pressed down (arrows 66) and theframe 64 unit may be pulled away from the power sub-assembly 12 andvertically pivoted upwards on a horizontal axis (arrow 68).Additionally, a top cover 68 of the control sub-assembly 14 may beunlocked from the power sub-assembly 12 by pressing down and sliding thetop cover 68 away from the power sub-assembly 12 (arrows 70), as shownin FIG. 7.

After the control sub-assembly 14 and the power sub-assembly 12 havebeen detached, the control sub-assembly 14 may be removed from the powersub-assembly 12, as shown in FIG. 8. In some embodiments, after the topcover 68 is unlocked and/or the catches 62 are released, the controlsub-assembly 14 is removed by holding its sides firmly (arrows 72) andpulling the control sub-assembly 14 away from the power sub-assembly 12(arrow 74).

FIG. 9 is a perspective view of inserting an interface connector 76 forthe communication sub-assembly 46 into a header 78 located at the backof the control sub-assembly 14. The interface connector 76 may enabledata to be sent between the communication sub-assembly 46 and thecontrol sub-assembly 14 so that external devices connected to thecommunication sub-assembly 46 can communicate with the controlsub-assembly 14. Also, in some embodiments, the interface connector 76may aid in securing the communication sub-assembly 46 to the controlsub-assembly 14. The interface connector 76 may be secured into theheader 78 by pressing the interface connector 76 into the header 78.

Once the interface connector 76 is in place, the communicationsub-assembly 46 may be installed, as shown in FIG. 10. FIG. 10 is aperspective view of installing the communication sub-assembly 46 byaligning it with the interface connector 76 of the control sub-assembly14 and connecting the two. In some embodiments, the communicationsub-assembly 46 may be pressed down onto the interface connector 76until the communication sub-assembly 46 snaps into the back of thecontrol sub-assembly 14. After the communication sub-assembly 46 isinstalled in the control sub-assembly 14, the power sub-assembly 12 maybe reattached to the control sub-assembly 12.

Then, the communication sub-assembly 46 may be connected to the network.In some embodiments, connecting the communication sub-assembly 46 to thenetwork may include connecting a 5-pin linear plug to a network cable(e.g., DeviceNet cable). The 5-pin linear plug may then be inserted intoa mating socket of the communication sub-assembly and secured viahardware (e.g., screws). The power may be reconnected and supplied viathe power sub-assembly 12. The communication sub-assembly 46 receivesits power from the connected control sub-system 14, power sub-assembly12, and network.

FIG. 11 is a top view of the communication sub-assembly 46 includingvarious components in accordance with an embodiment. As illustrated, thecommunication sub-assembly 46 includes node address/rate switches 78, acommunication card drive header 80, status indicators 82, terminals 84,and a network connector 86. In particular, the node address/rateswitches 78 may be used to set the node address and network data rate.The communication card-drive header 80 may include a 40-pin, double-rowshrouded female header that is used with the interface connector 76 toconnect this header 80 to the header 78 on the drive (e.g., controlsub-assembly 14). The status indicators 82 may include threelight-emitting diodes (LEDs) that indicate the status of the connecteddrive, communication sub-assembly 46, and network. In some embodiments,the status indicators 82 display the status through apertures in thefront panel of the control sub-assembly 14. Also, the terminals 84provide a ground for communication bus cable shields. In addition, thenetwork connector 86 may include a 5-pin connector to which a 5-pinlinear plug can be connected. However, it should be appreciated thatother pin connectors may be used. In some embodiments, the networkconnector 86 is used to provide access to a DeviceNet, Profibus,EtherNet/IP, and/or Modbus network protocols. As may be seen, thecommunication sub-assembly 46 includes a groove 88 that is configured tofit around the mating connectors 20 and 22 of the power subassembly 12and the control subassembly 14 when they are connected. As a result, thecommunication sub-assembly 46 may be positioned between the powersubassembly 12 and the control subassembly 14 when the motor drivesystem is fully assembled. However, it should be understood, that insome embodiments, the communication sub-assembly 46 is only physicallyand electrically coupled to the control sub-assembly 14. That is, thecommunication sub-assembly 46 does not send any data directly to thepower sub-assembly 12, nor is the communication sub-assembly physicallycoupled to the power sub-assembly 12.

FIG. 12 is an exemplary illustration of a single-drive mode where asingle network node consists of a single motor drive system 10 with thecommunication sub-assembly 46. The high speed drive serial interface(HSDSI) protocol supported by the communication sub-assembly 46 mayenable operating in the single-drive mode. The motor drive systems 10including the communication sub-assembly 46 running in single-drive modecan control and communicate with other drives. As depicted, numerousdrive systems 10 (e.g., 5), each representing an individual networknode, are connected via a network 90 (e.g., DeviceNet, EtherNet/IP,Profibus, Modbus).

The communication sub-assembly operating via the HSDSI protocol alsosupports a multi-drive operation mode, where HSDSI passes data for up tofive drives to the drive containing the communication sub-assembly 46,as shown in FIG. 13. The multi-drive mode depicted shows a singlenetwork node 92 consists of one to five drives where the first drive 92includes the communication sub-assembly 46. The first drive 92 isconsidered the “master” drive 92 and the connected drives are consideredthe “slave” drives 94. The slave drives 94 may be daisy-chain connectedand may not include the communication sub-assembly 46. The “master”drive 92 may split the information between the drives 94 and forward theinformation to each individual “slave” drive 94 over a traditional DSIcommunication bus 96. HSDSI allows for faster communication (3 Mbps vs.19,200 bps with other systems), provides the user with betterinformation about communication status, and simplifies installation andwiring (in multi-drive mode, communication sub-assembly 46 does not haveto be mounted outside of the drives and wired directly to thecommunication bus between the drives).

FIG. 14 is a table depicting a HSDSI packet format specification 100, inaccordance with an embodiment. In one embodiment, HSDSI packets are sentat a fixed baud rate of 3 Mbps, with 1 stop bit, 2 stop bits, and noparity. Bits may be sent least significant bit (LSB) first within eachbyte. As depicted in the specification table 100, C→D indicatescommunication sub-assembly 46 to drive (control sub-assembly 14), D→Cindicates drive to communication sub-assembly 46. “Single” and “multi”in the specification table 100 indicate single vs. multi-drive mode.Byte order of all multi-byte fields is big-endian (most significant byte(MSB) first). Pad 101 words may be sent as zero and ignored on receive.The total packet size is 170 bytes, which takes 0.623 ms to transmit ifthere are no delays between bytes.

In some embodiments, the “master” of the communication interface is thecommunication sub-assembly 46. At power-up, the communicationsub-assembly 46 transmits the first packet. As soon as the drivefinishes receiving that packet and confirms a valid cyclic redundancycheck (CRC), the drive transmits its own packet to the communicationsub-assembly 46. As soon as the communication sub-assembly 46 finishesreceiving that packet and confirms a valid CRC, the communicationsub-assembly 46 transmits another packet to the drive. The drive andcommunication sub-assembly 46 continue exchanging packets in thismanner, with low-level and high-level timeout mechanisms available,described below, to reestablish communications in the event of data orsynchronization errors or temporary communication losses.

In some embodiments, the drive may not use any data corresponding to afield with its “control valid” bit 102 turned off and neither may thecommunication sub-assembly 46. The communication sub-assembly 46 mayonly turn on the control valid bits 102 at the time it actually istaking control of the corresponding data. Discussed below are “controlvalid” bit 102 field definition and examples.

In a presently contemplated embodiment, while a “lock I/O image” bit isset, the drive may maintain or “lock” the meaning of all fields in the“control data” 103 image, including the parameters pointed to bydatalinks, logic command bits (e.g., “lock” the drive into velocity orposition mode), and reference values because a network I/O connection islabeling the fields to the user as having the currently configuredmeaning. The drive may not allow the communication sub-assembly 46 orany other source of configuration changes to change the meaning of anypart of the HSDSI “control data” 103 image.

In this embodiment, the lock I/O image bit will only change state whenthe drive is reset or power cycled. While this bit is off, the drive mayignore any control valid bits and messaging requests received. Whilethis bit is off, the drive may show the port representing thecommunication sub-assembly 46 as “disabled” to a HIM and software tools,even if a communication sub-assembly 46 is detected in that port. Whilethis bit is off, the drive's message router may provide an errorresponse to any messaging request whose destination is the communicationsub-assembly 46, unless a response is necessary to display the port asdisabled.

A single-drive I/O bit will only change state when the drive is reset orpower cycled. If a “data from net valid” bit for single driveapplications or a “logic command/reference to drive valid” bit formulti-drive applications is set, the drive may supply the associateddata in this packet to the destination drive. If this bit is cleared,the drive may not use the data. This bit is used in both single andmulti-drive modes. In either mode the drive may ignore information fromthe corresponding fields if this bit is not set. For example, if thereis logic command/reference data for multi-drive drop #1, but the bit isnot set, that command/reference will not be forwarded to multi-drivedrop #1.

For the communication sub-assembly 46 to perform a communication or idlefault action of “fault”, the communication sub-assembly 46 sets all fiveof the valid bits to 0. For the communication sub-assembly 46 to performother fault actions of “stop”, “hold last”, “zero data”, or “faultconfig,” the communication sub-assembly 46 may continue to set the bitsthat were already set, and may simply provides the logic command,reference, and datalink data corresponding to the desired fault action,until a running network I/O connection resumes or there is an HSDSIcommunication loss.

If the control valid bit 102 transitions from set to cleared in singledrive mode, the drive may produce an “option card net loss” fault. Ifthe control valid bit 102 transitions from set to cleared, inmulti-drive mode, the destination master drive may produce an “optioncard net loss” fault, and the destination slave drives may produce a“DSI net loss” fault. To forward a fault request to the slave drive, themaster drive may enqueue a write message to a destination register ofthe slave drive that sets its “force comm loss event” bit. Note thatthis may also be the method used by the master drive to communicate anHSDSI control timeout to the slave drives when operating in multi-drivemode.

A “data link to net valid” bit validity is based upon the datalinkselection parameter pointing to a valid parameter. If the communicationsub-assembly 46 receives a packet where a datalink being used in itsnetwork I/O image is invalid, the communication sub-assembly 46 dropsits network I/O connection.

A “logic status/feedback from drive valid” bit that is set in the driveto communication sub-assembly 46 transmissions may indicate that theslave drive is configured and responding properly on a certain network(e.g., Modbus).

The communication sub-assembly 46 may ignore “logic status/feedbackvalid for drive #0” if drive #0 cannot send valid logic status/feedbackthat indicates that the HSDSI link has failed, which a timeout willhandle. Essentially the HSDSI communication sub-assembly 46 link beingvalid indicates that the logic status/feedback from drive #0 is valid.If the HSDSI connection is lost, the communication sub-assembly 46 mayshut down its network I/O connection, instead of when all multi-drivedrops are lost.

If the communication sub-assembly 46 loses the datalink “from net”information from the upstream network, it may continue sending the mostrecent data for the datalinked parameters, keeping the control valid bit102 set to 1. If the communication sub-assembly 46 wants the drive tofault then it will set the control valid bit 102 to zero.

Other field definitions included in the specification table 100 include“cmd” 104, which stands for command, “sts” 105, which stands for logicstatus, “ref” 106, which stands for reference, and “fdbk” 107, whichstands for feedback. For multi-drive, the 0 through 4 digits indicatewhich drive is the source or destination of the control data 103.

For messaging, the comm-initiated transaction portion 108 of the packetcontains a place where the communication card can transmit messagingrequests, or the drive can transmit responses to the communicationcard's previous requests. The drive-initiated transaction portion 109 ofthe packet contains a place where the drive can transmit messagingrequests, or the communication card can transmit responses to thedrive's previous requests.

Data transmitted in the message buffer remains in the buffer untilanother transaction occurs. This allows recovery from an error intransmitting or receiving a packet containing a messaging request orresponse.

For all messaging buffers, “seq” 110 refers to a messaging transactionsequence number. In some embodiments, at power-up and whenreestablishing communications after a control timeout occurs, before amessage request is available, the sender transmits a zero in “seq” 110field and all other fields relating to the message request, includingthe “lgth” 111, “addr” 112, and “func” 113 fields. When a messagerequest is available to transmit, the client device increments itstransmitted sequence number (rolling over from 0xFF to 0x01 to avoidreusing 0). The server device may not increment its transmitted sequencenumber until a response to that particular messaging request isavailable. Once the response is available, the server device may updateits transmitted sequence number to match the client device's sequencenumber. When the client device receives a matching sequence number, theclient device picks up the response to its message.

If at any time either the client device or the server device sees asequence number of zero, it should abort any messaging transaction inprogress at the time, reset its expected sequence number, and echo backa zero for its side of that messaging transaction. This mechanism allowsthe message originator to communicate a timeout and resynchronizewithout the risk of reusing the same sequence number as before thetimeout.

If at any time either the client device or the server device sees anunexpected sequence number (i.e., not the same sequence number as in themost recently received packet, and not the next number in the sequenceaccounting for rollover from 0xFF to 0x01), that side should abort anymessaging transaction in progress at the time, reset its expectedsequence number, and echo back a zero for its side of that messagingtransaction. This mechanism allows the two sides to quickly resolve asituation where there is disagreement about the messaging sequencenumber in use.

If there is a need to retry a message (e.g., after a router's or anapplication-layer timeout), the retried message receives a new sequencenumber just as if it were a brand-new messaging transaction.

For all messaging buffers, “lgth” 111 may refer to the total length ofthe protocol (e.g., Modbus) message in bytes, including the “addr” 112,“func” 113, and “data” 114 fields.

For all messaging buffers, “addr” 112 may refer to the destinationaddress of the messaging transaction. In single drive mode, in someembodiments, this may be 0xF8 for the drive, 0xF9 for the communicationsub-assembly 46, and 0xFA for the DSI peripheral. In some embodiments,the address of 0xFC is supported, which represents a common industrialprotocol (CIP) virtual port. In multi-drive mode, in some embodiments,this may be either 0 or 0xF8 for the master drive, and 1 through 4 forthe slave drives. The master drive may need to translate this address toa protocol (e.g., Modbus) address when forwarding the message over theprotocol.

For all messaging buffers, “func” 113 may refer to the protocol (e.g.,Modbus) or DSI function code for the messaging transaction. Note that inembodiments using HSDSI, control messages with function codes 0x7B and0x7C may not be used, since the control data 103 may be placed inanother location in the packet.

For all messaging buffers, “data” 114 may be 66 bytes in length, even ifthe actual protocol (e.g., Modbus) message contains fewer than 66 bytesof data. This keeps the packet size and format constant, enabling theuse of DMA-based transmissions and receives and simplifying processing.In some embodiments, the unused portion of the buffer may be populatedwith 0 values.

In some embodiments, the CRC 115 may include a standard Modbus CRC thatcovers the entire packet up to the point where the CRC begins (i.e., thepreceding 168 bytes).

FIG. 15 is a sequence diagram 116 of packet exchanges initiated by thecommunication sub-assembly 46 with the drive (control sub-assembly 14).To initiate communication with the drive, the communication sub-assembly46 may send an initial packet to start up the HSDSI interface without amessage request. The initial packet may include all 0 values for seq,lgth, addr, func, and data fields. Since there is no message requestfrom the communication sub-assembly 46, the drive 14 has no response.Then, in event 118 in the sequence diagram 116, the communicationsub-assembly 46 may send a first message request requesting to read thedrive's number of parameters register. The drive may respond nearimmediately by sending a response in event 120 indicating its number ofparameters. Next, in event 122, the communication sub-assembly 46 sendsa second message request to the drive 14. The drive 14 may not have aresponse ready yet so it responds with the data from the first response(event 124). This cycle may continue for some time until the response tothe message request is available. For example, in event 126, thecommunication sub-assembly 46 repeats the second message request to thedrive 14 and the drive responds with a second response including therequested data (event 128). Then, in event 129, the communicationsub-assembly 46 may send a third request and the sequence may continue.

FIG. 16 is a schematic diagram of timeouts 130 used by the controlsub-assembly 14 and the communication sub-assembly 46. The timeouts 130may include a DMA reset timeout 131, a control timeout 132, and amessage timeout 133. Both the control sub-assembly 14 (drive) and thecommunication sub-assembly 46 may utilize the three HSDSI relatedtimeout functionalities.

The DMA reset timeout 131 may be a low level timeout that simply keepstrack of the health of the HSDSI connection; its timeout action may beto reset the DMA to allow for attempts at re-syncing the HSDSIconnection. The control timeout 132 may only be active once valid I/Ohas been received through HSDSI, and will cause a drive fault indicatingthe loss of the HSDSI connection. The message timeout 133 may monitorthe DSI messaging time and attempt to inhibit degenerate messaging casesfrom clogging/breaking the DSI message router.

Diagnostic counters for the number of times that each of the types oftimeouts have occurred may be used. Suggested names are “DMA TimeoutCnt”, “Ctl Timeout Cnt”, and “Msg Timeout Cnt”.

On the control sub-assembly 14 (drive) side, the DMA reset timeout 131may be used to ensure that the low level HSDSI communication interfaceis operating correctly, and that both sides are still in sync. This isused because of the functionality of the DMA. In some embodiments, oneway to recover from a drive-option HSDSI protocol breakdown is tocompletely reset and reinitialize the DMA. This timeout 131 may hingeupon receiving packets with valid CRCs. If no packet with a valid CRC isreceived in a configurable amount of time (e.g., 25 ms) duration thedrive's DMA will be reset. The drive may then wait for the communicationsub-assembly 46 to reinitiate the HSDSI communications with the same oran updated message that the communication sub-assembly 46 was attemptingto send before the timeout.

The control timeout 132 may be started when an HSDSI packet with a validCRC is received by the drive. If a certain amount of time (e.g., 100 ms)passes and no packet with a valid CRC is received then the drive may logan HSDSI communication fault. The drive may also stop sending andprocessing received packets for a period of time (e.g., at least 100 ms)to force the communication sub-assembly 46 to recognize its own controltimeout. Then, the communication sub-assembly 46 may reinitialize theinterface as it does at power-up, including setting both messagesequence count fields back to zero. The drive may also enqueue networkloss fault messages to the multi-drive drops. Note that, in someembodiments, the slave drives may show a DSI net loss fault. The controltimeout period may allow the DMA reset timeout 131 at least two attemptsto reset and restart HSDSI communications.

A messaging timeout 133 may attempt to inhibit the DSI router fromhanging in an event where a message query makes it to the router, butthe response never gets formed. This timeout 138 may monitor the amountof time that any router is in a busy state. In some embodiments, if anyrouter is busy for one second or longer, the source and destinationrouters for that query will be reset to their idle state, and theportion of the drive 14 firmware that initiated the message will beinformed of the timeout error so that it can pass the error message backto the originator.

Turning to the timeouts used by the communication sub-assembly 46, sincethe communication sub-assembly 46 is the master of the interface in someembodiments, the communication sub-assembly 46 is responsible forinitiating communications with the drive 14. Once the communicationsub-assembly 46 is ready to initialize the HSDSI interface, it sends anHSDSI packet to the drive, even if there is no control or messaging dataready at that time. The communication sub-assembly 46 will send packetsto the drive at least within a minimum rate to assure the health of theinterface even if there is not an I/O connection active. Once there iscontrol data 103 to be sent, the communication sub-assembly 46 may sendthe most recent command/reference.

The communication sub-assembly 46 has a similar low level timeout 131 tothe drive that resets the DMA, re-initializes the HSDSI communications,and begins transmitting a packet to the drive, if no packets with avalid CRC have been received within the timeout period. In someembodiments, a different timeout period than the drive 14 may be used toavoid both devices continuously resetting in phase with each other.

The communication sub-assembly 46 also has a control timeout 132 of aconfigurable amount of time (e.g., 100 ms), similar to the drive. If thecommunication sub-assembly 46 has started receiving control data 103with one or more control valid bits set, and either a future receivedpacket has a control valid bit transitioning from set to clear or 100 msgoes by without receipt of another packet, the communicationsub-assembly 46 may declare a control timeout 130. It may stop sendingand processing received packets for at least 100 ms to force the driveto recognize its own control timeout, then clears its control data 103valid bits 102 and reinitializes the interface as it does at power-up,including setting both message sequence count fields back to zero. Thecommunication sub-assembly 46 should also take the appropriate action onits network interface, for example dropping the network I/O connection,if there is an HSDSI communication loss.

The communication sub-assembly 46 messaging client may implement amessaging timeout 133 to inhibit the messaging client from hanging dueto not receiving a response to a message it has sent. This timeout 133may monitor the amount of time since the messaging request was firsttransmitted, and continues until a matching response is received. Insome embodiments, if the message is pending for one second or longer,the communication sub-assembly 46 sets the communicationsub-assembly-originated message sequence number to zero to indicate tothe drive 14 that the messaging request is being aborted. The portion ofthe communication sub-assembly 46 firmware that initiated the messagewill be informed of the timeout 133 error so that it can pass the errormessage back to the originator.

FIG. 17 is a flow diagram of a process 134 for a messaging resetsequence initiated by the communication sub-assembly 46 and FIG. 18 is aflow diagram of a process 192 for a messaging reset sequence initiatedby the control sub-assembly 14. It should be noted that the HSDSIinterface defines two messaging channels: option card-initiated anddrive-initiated (e.g., communication sub-assembly-initiated and controlsub-assembly-initiated). The two channels can be reset independently ofeach other, although lost HSDSI messages (DMA timeout) may apply to bothchannels simultaneously. The option card (e.g., communicationsub-assembly 46) is assumed to be the HSDSI master, and the drive (e.g.,control sub-assembly 14) is the HSDSI slave. In some embodiments, themain difference between the master and the slave is that the masteralways transmits a duplicate of the previous transmitted messageimmediately following a low level receive timeout (e.g., DMA timeout),whereas such a timeout causes the slave to simply reset its receiveprocess, wait for another HSDSI message, and then respond.

A messaging channel can be reset from either side. When one side (i.e.,master or slave) wants to reset a messaging channel, it first aborts anyupstream transaction that might be in progress on its own side thensends an HSDSI message with the message sequence number in theappropriate messaging segment set to 0. The other side is expected torespond to the reception of the 0 message sequence number by abortingits own upstream transaction and sending a reply message also with amessage sequence number of 0. In some embodiments, the 0 messagesequence number is only used for channel reset, and it is not usedduring normal transactions.

In some embodiments, the two messaging channels may be handledidentically on each side. However, the handling on the slave side candiffer from the handling on the master side. Also, when one side of thechannel is reset from the other side, it may send a response HSDSImessage before the abort of its upstream transaction can be completed.Therefore, the reset scheme may support multiple message exchangesbetween the initial 0 message sequence number transmitted by the siderequesting the reset and the 0 message sequence number responsetransmitted by the other side. At the end of the channel reset process,either side may transmit a new messaging request (i.e., change theoutgoing message sequence number from 0 to 1). For each channel, oneside (the client side) will actually transmit such a request, but thechannel reset protocol works either way.

The reset process may be completed on one side after one of thefollowing sequences occurs:

a.

-   -   Receive Message Sequence Number==0 without a receive timeout.    -   Transmit Message Sequence Number=0    -   Receive another message without a receive timeout. This message        is processed as a normal incoming message, and the received        Message Sequence Number is not necessarily 0.

b.

-   -   Transmit Message Sequence Number=0    -   Receive Message Sequence Number==0 without a receive timeout.

The following flow diagrams in FIGS. 17 and 18 start at the point whereone side of the messaging channel is ready to transmit a new message.There are two entry points for each flow diagram: one for normaltransmits, and the other for the case where the side doing the transmitwants to command a reset of the channel. The flow diagrams do not givedetails about the handling of “normal” messages.

It should be noted that, in the flow diagrams, “TX 0” means “Transmit anHSDSI message containing a message sequence number of 0 in theappropriate messaging segment”. “TX n” means “Transmit an HSDSI messagethat does not contain a message sequence number of 0 in the appropriatesegment”. It should be apparent from context whether the outgoingsegment should be an exact duplicate of the previous outgoing segment.“RX 0?” means “did the HSDSI message just received contain a messagesequence number of 0 in the appropriate messaging segment.” “RX0 Flag”and “TX0 Flag” are global variables used for the scheme. “RX Timeout” isthe low level receive timeout on the entire HSDSI message (also known as“DMA timeout 131”). The timeout 131 may apply to both messaging channelssimultaneously.

Beginning first with FIG. 17, which includes the flow diagramillustrating the option card-initiated message reset sequence, andfocusing on the entry point 136 where the master is performing normaltransmissions, the process 134 includes the communication sub-assembly46 clearing the response message sequence number set to 0 flag (processblock 138) and transmitting an HSDSI message that does not contain amessage sequence number of 0 in the appropriate segment (process block140). The communication sub-assembly 46 then waits for to receive anHSDSI response (process block 142) and determines whether there is a DMAtimeout 131 (decision block 144). If there is a timeout, then theprocess 134 returns to transmitting an HSDSI message that does notcontain a message sequence number of 0 in the appropriate segment(process block 140). If there is not a timeout, then the process 134includes determining whether the HSDSI message just received contains amessage sequence number of 0 in the appropriate messaging segment(decision block 146). If not, then the process 134 includes a normalcase and process the response and sends another normal transmission bystarting at point 136 again. If response message sequence number is setto 0, then the process includes setting the response message sequencenumber 0 flag in process block 148. Then, the process 134 includesdetermining whether there is a transaction in progress (decision block150).

If there is a transaction in progress, then the process 134 includesinitiating master-side upstream transaction abort (process block 152)and transmitting the last HSDSI message that does not contain a messagesequence number of 0 in the appropriate segment (process block 154).Next, the process 134 includes waiting for the response (process block156) and determining whether there is a DMA timeout (decision block158). If there is a timeout, then the response message sequence number 0flag is cleared (process block 160) and the process 134 returns totransmitting the last HSDSI message that does not contain a messagesequence number of 0 in the appropriate segment (process block 154). Ifthere is not a timeout, a decision is made whether the HSDSI messagejust received contain a message sequence number of 0 in the appropriatemessaging segment (decision block 162). If so, then the response messagesequence number 0 flag is set (process block 164) and, if not, then theresponse message sequence number 0 flag is cleared (process block 166).Either way, the process 134 continues to determine whether thetransaction abort is complete (decision block 168). If it is notcomplete, then the process 134 returns to transmitting the last HSDSImessage that does not contain a message sequence number of 0 in theappropriate segment (process block 154). If the transaction abort iscomplete, then the process 134 transmits an HSDSI message containing amessage sequence number of 0 in the appropriate messaging segment(process block 170). Then, the process 134 waits for a response (processblock 172) and determines whether there is a DMA timeout 131 (decisionblock 174). If there is a timeout, the response message sequence number0 flag is cleared (process block 176), and then the process 134transmits an HSDSI message containing a message sequence number of 0 inthe appropriate messaging segment (process block 170), and the processcontinues from block 170. If there is not a timeout, then the process134 determines whether the response message sequence number 0 flag isset (decision block 178). If so, the reset is complete and the responseis processed normally, then the process 134 returns to normaltransmission at point 136. If not, a determination is made whether theHSDSI message just received contain a message sequence number of 0 inthe appropriate messaging segment (decision block 182). If so, the resetis complete and response processing is complete, so the process 134returns to normal transmission at point 136 (process block 184). If not,the process 134 clears the response message sequence number 0 flag atprocess block 176 and continues processing back to process block 170.

If there is not a transaction in progress, the process 134 transmits anHSDSI message containing a message sequence number of 0 in theappropriate messaging segment (process block 170) and continues toprocess block 172, as described above.

Starting from the entry point 186 where the master sends the resetrequest, the process 134 aborts the master-side upstream transaction(client or server) (process block 188). Then, the response messagesequence number 0 flag is cleared (process block 190). The process 134transmits an HSDSI message containing a message sequence number of 0 inthe appropriate messaging segment (process block 170) and continues toprocess block 172, as described above.

FIG. 18 illustrates the flow diagram of a process 192 for the slave side(control sub-assembly 14, referred to as drive below) initiated messagereset sequence. Starting at entry point 194 where the slave and masterare performing normal transmissions, the process 192 includes the driveclearing the received message sequence number set to 0 flag (processblock 196) and transmitting an HSDSI message that does not contain amessage sequence number of 0 in the appropriate segment (process block198). The drive then waits to receive an HSDSI response (process block200) and determines whether there is a DMA timeout 131 (decision block202). If there is a timeout, then the process 192 returns totransmitting an HSDSI message that does not contain a message sequencenumber of 0 in the appropriate segment (process block 200). If there isnot a timeout, then the process 192 includes determining whether theHSDSI message just received contains a message sequence number of 0 inthe appropriate messaging segment (decision block 204). If not, then theprocess 192 includes a normal case and processes the response and sendsanother normal transmission by starting at point 194 again. If messagesequence number is set to 0, then the process includes setting theresponse message sequence number to 0 flag in process block 206. Then,the process 192 includes determining whether there is a transaction inprogress (decision block 208).

If there is a transaction in progress, then the process 192 includesinitiating slave-side upstream transaction abort (process block 210) andtransmitting the last HSDSI message that does not contain a messagesequence number of 0 in the appropriate segment (process block 212).Next, the process 192 includes waiting for the response (process block214) and determining whether there is a DMA timeout (decision block216). If there is a timeout, then the response message sequence number 0flag is cleared (process block 218) and the process 192 returns towaiting for the response (process block 214). If there is not a timeout,a decision is made whether the HSDSI message just received contain amessage sequence number of 0 in the appropriate messaging segment(decision block 218). If so, then the response message sequence number 0flag is set (process block 220) and, if not, then the response messagesequence number 0 flag is cleared (process block 222). Either way, theprocess 192 continues to determine whether the transaction abort iscomplete (decision block 224). If it is not complete, then the processreturns to transmitting the last HSDSI message that does not contain amessage sequence number of 0 in the appropriate segment (process block212) and the process 192 continues accordingly, as described above. Ifthe transaction abort is complete then the process 192 sets thetransmission message sequence number 0 flag and transmits an HSDSImessage containing a message sequence number of 0 in the appropriatemessaging segment (process block 226). Then, the process 192 waits for aresponse (process block 228) and determines whether there is a DMAtimeout (decision block 230). If there is a timeout, the responsemessage sequence number 0 flag is cleared, the transmission messagesequence number 0 flag is cleared (process block 232), and then theprocess 192 returns to waiting for a response (process block 228). Ifthere is not a timeout, then the process 192 determines whether theresponse message sequence number 0 flag is set and whether thetransmission message sequence number 0 flag is set (decision block 234).If so the reset is complete at point 236 and the response is processednormally, then the process 192 returns to normal transmission at point194. If not, a determination is made whether the HSDSI message justreceived contain a message sequence number of 0 in the appropriatemessaging segment (decision block 238). If not, the response messagesequence number 0 flag is cleared (process block 240) and the process192 returns to process block 226 and continues to process accordingly,as described above. If the HSDSI message just received does contain amessage sequence number of 0 in the appropriate messaging segment, thena determination is made whether the response message sequence number 0flag is clear and the transmission message sequence number 0 flag is set(decision block 242). If so, then the reset is complete at point 244 andreceived message processing is complete and the process 192 returns tonormal transmission at point 194. If not, the response message sequencenumber 0 flag is set (process block 246) and the process 192 returns toprocess block 226 to continue processing accordingly, as describedabove.

If there is not a transaction in progress, the process 192 sets thetransmission message sequence number 0 flag and transmits an HSDSImessage containing a message sequence number of 0 in the appropriatemessaging segment and (process block 226) and continues to process block228, as described above.

Starting from the entry point 248 where the slave sends the resetrequest, the process 192 aborts the slave-side upstream transaction(client or server) (process block 250). Then, the response messagesequence number 0 flag is cleared (process block 252). The process 192sets the transmission sequence message number 0 flag, transmits an HSDSImessage containing a message sequence number of 0 in the appropriatemessaging segment (process block 226), and continues to process block228, as described above.

To further describe how the communication sub-assembly 46 uses the HSDSIprotocol, the discussion now focuses on startup and login handling. Atstartup, in some embodiments, the communication sub-assembly 46 isexpected to send one HSDSI packet with no control valid bits set andcontaining no message request. The response from the drive 14 to thatpacket may contain the “interface enabled” bit for the communicationsub-assembly 46 to check its state. If the “interface enabled” bit isoff, the communication sub-assembly 46 may not send further packets. Thecommunication sub-assembly 46 may continue to send packets (e.g., atintervals longer than when communications are active, but usually notlonger than a period of time (100 ms) to avoid missing a drive reset) sothat the communication sub-assembly 46 may detect when the drive resets,and then attempt to reestablish communications. After login on HSDSI, anetwork I/O connection to the communication sub-assembly 46 may not bepresent. When the network connection opens at a later time, thecommunication sub-assembly 46 may set the appropriate control valid bitsand begins forwarding the control data 103 to the drive.

Focusing now on updating the firmware, software, or some combinationthereof (referred to as “flashing”), in multi-drive mode, the ability toflash either the master or any slave drive may not be present. Toaccomplish this, communication sub-assemblies 46 may not present CIPidentity instances for multi-drive drives on the network interface 50.In some embodiments, while the communication sub-assembly 46 is beingflashed over its network connection, the HSDSI connection may bedropped. The resulting drive fault may be expected. In some embodiments,while the drive 14 is being flashed through embedded Ethernet or DSI,the HSDSI connection may also be dropped. While the drive 14 is beingflashed through the communication option, HSDSI may stay online. Anactive flash update is signified by the fact that a flash message(function 0x63) is the active messaging transaction being sent betweendevices. When the drive 14 sees the first flash message, the drive 14may generate a net loss fault if the drive was receiving any controldata from the control sub-assembly 46.

While processing a flash message, both messaging 133 and control 132timeouts may be suspended. DMA reset timeout 131 periods may be relaxedto account for flash programs and erases. That is, the DMA timeout 131may be suspended during flash programming operations and restart orcontinue when done accessing the flash chip.

At the end of a flash update, the drive 14 and communicationsub-assembly 46 may either explicitly reset, or the control timeout 132may resume after no flash messages have been sent for some time, and thecontrol timeout 132 may cause both devices to reinitialize andreestablish HSDSI communications.

While only certain features of the present techniques have beenillustrated and described herein, many modifications and changes willoccur to those skilled in the art. It is, therefore, to be understoodthat the appended claims are intended to cover all such modificationsand changes as fall within the true spirit of the present disclosure.

The invention claimed is:
 1. A motor drive system comprising: a modularpower subassembly controllable to provide controlled frequency AC powerto an electric motor; a modular control subassembly separable from themodular power subassembly that, in operation, applies control signals tothe modular power subassembly for controlling the provided power; and anadd-on communication subassembly positionable between the modular powersubassembly and the modular control subassembly, comprising a componentphysically separate from the modular control subassembly, andelectrically coupled to the modular control subassembly for providingcommunication between the modular control subassembly and at least oneexternal device when the modular control subassembly is secured to themodular power subassembly and the add-on communication subassembly iscoupled to the modular control subassembly.
 2. The system of claim 1,wherein the modular power and control subassemblies comprise matingmulti-conductor connectors that mate when the modular controlsubassembly is attached to the modular power subassembly to conveysignals between the modular power and control subassemblies.
 3. Thesystem of claim 2, wherein the add-on communication subassembly isconfigured to fit around the mating multi-conductor connectors when themodular control subassembly is attached to the modular powersubassembly.
 4. The system of claim 1, wherein the add-on communicationsubassembly is attached to the modular control subassembly prior tomating the modular control subassembly with the modular powersubassembly.
 5. The system of claim 1, comprising an adapter connectorfor connecting the add-on communication subassembly to the modularcontrol subassembly.
 6. The system of claim 1, wherein the add-oncommunication subassembly is not electrically coupled to the modularpower subassembly and does not directly convey signals with the modularpower subassembly.
 7. The system of claim 1, wherein the add-oncommunication subassembly receives power from a connected network, themodular control subassembly that is connected to the modular powersubassembly, or some combination thereof.
 8. The system of claim 1,wherein the add-on communication subassembly comprises status indicatorsconfigured to display a status of the add-on communication subassembly,the modular control subassembly, network communications, or somecombination thereof, through apertures in a front panel of the modularcontrol subassembly.
 9. The system of claim 1, wherein the add-oncommunication subassembly comprises a communications module configuredto communicate with the at least one external device via EtherNet/IP.10. A motor drive system comprising: an add-on communication subassemblyconfigured to be positioned between a modular control subassembly and amodular power subassembly of the motor drive system and comprising acomponent physically separate from the modular control subassembly,wherein the add-on communication subassembly is electrically coupled tothe modular control subassembly and provides communication between themodular control subassembly and external devices when the modularcontrol subassembly is secured to the modular power subassembly and theadd-on communication subassembly is coupled to the modular controlsubassembly.
 11. The system of claim 10, wherein the add-oncommunication subassembly is physically mounted to the modular controlsubassembly between the modular power subassembly and the modularcontrol subassembly.
 12. The system of claim 10, wherein the modularpower and control subassemblies comprise mating multi-conductorconnectors that mate when the modular control subassembly is attached tothe modular power subassembly to convey signals between the modularpower and control subassemblies.
 13. The system of claim 12, wherein theadd-on communication subassembly is configured to fit around the matingmulti-conductor connectors when the modular control subassembly isattached to the modular power subassembly.
 14. The system of claim 10,comprising an adapter connector for connecting the add-on communicationsubassembly to the modular control subassembly.
 15. The system of claim10, wherein the add-on communication subassembly receives power from aconnected network, the modular control subassembly that is connected tothe modular power subassembly, or some combination thereof.
 16. Thesystem of claim 10, wherein the add-on communication subassemblycomprises status indicators configured to display a status of the add-oncommunication subassembly, the modular control subassembly, networkcommunications, or some combination thereof, through apertures in afront panel of the modular control subassembly.
 17. A motor drivesystem, comprising: a modular power subassembly controllable to providecontrolled frequency alternating current power to an electric motor; amodular control subassembly separable from the modular power subassemblyand that, in operation, applies control signals to the modular powersubassembly for controlling the provided power via a first matingconnector of the modular power subassembly connected to a second matingconnector of the modular control subassembly; and an add-oncommunication subassembly comprising a component physically separatefrom the modular control subassembly and only physically coupled andelectrically coupled to the modular control subassembly for providingcommunication between the modular control subassembly and at least oneexternal device when the modular control subassembly is secured to themodular power subassembly and the add-on subassembly is coupled to themodular control subassembly, wherein the add-on communicationsubassembly is configured to fit around the mated first and secondmating connectors when the modular control assembly and the modularpower subassembly are attached so that the communication subassembly ispositioned between the modular control subassembly and the modular powersubassembly.
 18. The system of claim 17, comprising an adapter connectorfor connecting the add-on communication subassembly to the modularcontrol subassembly.
 19. The system of claim 18, wherein the add-oncommunication subassembly comprises node address/rate switchesconfigured to set a node address and network data rates, a communicationcard drive header configured to attach to the adapter connector, statusindicators configured to display a status of the communicationsubassembly, the modular control subassembly, network communications, orsome combination thereof, and a network connector configured to provideaccess to one or more network protocols.
 20. The system of claim 17,wherein the add-on communication subassembly is configured to conveycontrol and message data between the modular control subassembly and theat least one external device.